Tight control over the delivery of insulin in both type I diabetes (usually juvenile onset) and type II diabetes (usually late adult onset), has been shown to improve the quality of life as well as the general health of these patients. Insulin delivery has been dominated by subcutaneous injections of both long acting insulin to cover the basal needs of the patient and by short acting insulin to compensate for meals and snacks. Recently, the development of electronic, external insulin infusion pumps has allowed the continuous infusion of fast acting insulin for the maintenance of the basal needs as well as the compensatory doses (boluses) for meals and snacks. These infusion systems have shown to improve control of blood glucose levels. However, they suffer the drawbacks of size, cost, and complexity. For example, these pumps are electronically controlled and must be programmed to supply the desired amounts of basal and bolus insulin. This prevents many patients from accepting this technology over the standard subcutaneous injections.
Hence, there is a need in the art for a convenient form of insulin treatment which does not require significant programming or technical skills to implement to service both basal and bolus needs. Preferably, such a treatment would be carried out by an infusion device that is simple to use and mechanically driven negating the need for batteries and the like. It would also be preferable if the infusion device could be directly attached to the body and not require any electronics to program the delivery rates. The insulin is preferably delivered through a small, thin-walled tubing (cannula) through the skin into the subcutaneous tissue similar to technologies in the prior art.
While the idea of such a simple insulin delivery device is compelling, many obstacles must be overcome before such a device may become a practical realty. One problem resides in insulin supply. Patients vary greatly on the amount of insulin such a device must carry to provide treatment over a fixed time period of, for example, three days. This is one environment where one size does not fit all.
Another problem is with cannula deployment to support insulin delivery. Cannula deployment to support delivery of the insulin beneath the patient's skin must be made easy and convenient. This is not as easy as it seems because cannula deployment, as generally and currently performed in the art, requires insertion of a cannula-carrying needle into the patient and then retraction of only the needle to leave the cannula in place beneath the patient's skin.
When needles are introduced beneath a patient's skin, during an injection, for example, it is well known that the pain associated with the injection may be reduced by forming a fold in the skin at the injection site prior to the injection. The fold of skin can also increase the probability that only soft tissue will be affected during the injection. However, the forming of such a skin fold when the needle is also being driven through an associated device, such as in infusion device, for example, to deliver a cannula to a deployed position extending from the device to beneath the skin is not readily possible. The reason for this is that in such cases, the device is already adhered to the skin and covers the injection site, making it virtually impossible to form a desired skin fold to receive the needle and cannula. As will be seen subsequently, the present invention addresses these and other issues toward providing a simple, practical, reliable and relatively pain-free deployment of a cannula beneath the skin to support insulin delivery.